Surgical lasers are now commonly used in a variety of ophthalmic applications, including the diagnosis and treatment of ocular diseases, as well as the diagnosis and correction of optical deficiencies. As an example, corneal reshaping procedures using lasers, such as the well known LASIK procedure, are now widely available. In all of these procedures, the surgical laser is chosen as the tool of choice because of the ability of the laser to be accurately focused on extremely small amounts of ocular tissue. In addition, the ability of the laser to be guided to prescribed locations within the eye with precision and reliability has enabled a whole new class of ophthalmic procedures that require nothing short of pinpoint accuracy. Unfortunately, movements of the eye relative to the laser source can undermine the accuracy of the laser and reduce the efficacy of the laser procedure.
With the above in mind, movements of the eye can be classified broadly into two groups, namely, voluntary movements and involuntary movements. Voluntary movements can often be almost completely eliminated in most patients by instructing the patient to concentrate (i.e. fixate) on a target such as a small light source. On the other hand, involuntary eye movements cannot be remedied by instruction, and as a consequence, they must be somehow controlled. Included in the involuntary eye movements are movements due to the patient's pulse, movements due to the patient breathing, and psychotic eye movements which can occur, for example, when a patient is startled.
It can be easily appreciated that these involuntary movements can have an adverse effect on a laser operation unless the movements are either compensated for, or effectively eliminated. With regard to the former, eye tracking systems have been proposed to compensate for eye movement during a procedure. In simple terms, these tracking systems measure movements of the eye during a procedure and provide a real time signal indicating eye position to the laser system. In response to the signal, the laser system moves, and in some cases reshapes, the laser beam to follow the movements of the eye. Unfortunately, these eye tracking systems tend to be overly complicated, and, as a practical matter, do not always provide the reliability that is required for certain types of procedures. For example, for procedures wherein the laser is configured to ablate and destroy selected tissue, an error or malfunction of the tracking system can result in the immediate destruction of non-target tissue.
Unlike eye tracking systems which attempt to compensate for eye movements, eye stabilization systems can be used to effectively eliminate eye movements, and are generally more reliable and less complicated than eye tracking systems. In addition to eliminating eye movement, some eye stabilization systems can be used to establish a desirable alignment between the eye and the laser source. Moreover, the eye stabilization element can be attached to the laser system to establish and maintain an optimal (and known) optical path length between the eye and laser system.
One factor that is worthy of consideration when contemplating the use of an eye stabilization and alignment device is the comfort and safety of the patient. In this regard, eye stabilization devices typically apply a mechanical pressure to the eye for the purpose of restraining the eye. Generally, this pressure is applied to the surface of the eye (i.e. the sclera, limbus or cornea). For obvious reasons, large pressures applied to the eye are often uncomfortable to the patient and can result in post-operative pain and scarring. Moreover, the pressure can cause damage to the eye by increasing the intra-ocular pressure of the eye to dangerous levels.
For some eye stabilizing devices, a stabilizing element is first attached to the eye and thereafter the stabilizing element is aligned with and attached to a coupler or adapter on the laser source. For these types of devices, the pressures exerted on the eye during both stabilization and coupling to the laser source must be considered. In addition to the constraints described above, an eye stabilizing and alignment device must also be positioned such that it does not interfere with the laser procedure. Specifically, this implies that opaque portions of the device do not lie along the laser delivery beam path.
With regard to the process of aligning and attaching an eye to a laser system, as indicated above, this procedure must be carried out carefully to avoid the exertion of dangerous pressure levels on the eye. Heretofore, these alignment and “docking” procedures have generally been done manually. Specifically, this means that the movement of the eye relative to the laser system has needed to be observed visually by the surgeon and controlled by the hand of the surgeon. In these procedures, movements of the eye must be accommodated and corrected for and this often results in a relatively slow, labor intensive procedure, the satisfactory performance of which is highly dependent on the skill and patience of the surgeon.
In light of the above, it is an objective of the present invention to provide a device and method for aligning a patient's eye relative to a laser system to facilitate an engagement between the eye and laser system. Another object of the present invention is to provide an automated device for aligning a patient's eye relative to a laser system which does not rely exclusively on human eye hand coordination. Yet another object of the present invention is to provide a device and method for aligning and engaging a patient's eye with a laser system without damaging the eye. Still another object of the present invention is to provide a device and method for aligning a patient's eye relative to a laser system that is easy to use, relatively simple to manufacture, and comparatively cost effective.